Julie Plet

Publications (2)14.54 Total impact

• Article: Two Direct Targets of Cytokinin Signaling Regulate Symbiotic Nodulation in Medicago truncatula.

  Federico Ariel, Marianne Brault-Hernandez, Carole Laffont, Emeline Huault, Mathias Brault, Julie Plet, Michael Moison, Sandrine Blanchet, Jean Laurent Ichanté, Mireille Chabaud, Sébastien Carrere, Martin Crespi, Raquel L Chan, Florian Frugier
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  ABSTRACT: Cytokinin regulates many aspects of plant development, and in legume crops, this phytohormone is necessary and sufficient for symbiotic nodule organogenesis, allowing them to fix atmospheric nitrogen. To identify direct links between cytokinins and nodule organogenesis, we determined a consensus sequence bound in vitro by a transcription factor (TF) acting in cytokinin signaling, the nodule-enhanced Medicago truncatula Mt RR1 response regulator (RR). Among genes rapidly regulated by cytokinins and containing this so-called RR binding site (RRBS) in their promoters, we found the nodulation-related Type-A RR Mt RR4 and the Nodulation Signaling Pathway 2 (NSP2) TF. Site-directed mutagenesis revealed that RRBS cis-elements in the RR4 and NSP2 promoters are essential for expression during nodule development and for cytokinin induction. Furthermore, a microRNA targeting NSP2 (miR171 h) is also rapidly induced by cytokinins and then shows an expression pattern anticorrelated with NSP2. Other primary targets regulated by cytokinins depending on the Cytokinin Response1 (CRE1) receptor were a cytokinin oxidase/dehydrogenase (CKX1) and a basic Helix-Loop-Helix TF (bHLH476). RNA interference constructs as well as insertion of a Tnt1 retrotransposon in the bHLH gene led to reduced nodulation. Hence, we identified two TFs, NSP2 and bHLH476, as direct cytokinin targets acting at the convergence of phytohormonal and symbiotic cues.
  The Plant Cell 09/2012; 24(9):3838-52. · 8.99 Impact Factor
• Article: Comparative Transcriptomic Analysis of Salt Adaptation in Roots of Contrasting Medicago truncatula Genotypes.

  Ons Zahaf, Sandrine Blanchet, Axel de Zélicourt, Benoît Alunni, Julie Plet, Carole Laffont, Laura de Lorenzo, Sandrine Imbeaud, Jean-Laurent Ichanté, Anouck Diet, Mounawer Badri, Ana Zabalza, Esther M González, Hervé Delacroix, Véronique Gruber, Florian Frugier, Martin Crespi
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  ABSTRACT: Evolutionary diversity can be driven by the interaction of plants with different environments. Molecular bases involved in ecological adaptations to abiotic constraints can be explored using genomic tools. Legumes are major crops worldwide and soil salinity is a main stress affecting yield in these plants. We analyzed in the Medicago truncatula legume the root transcriptome of two genotypes having contrasting responses to salt stress: TN1.11, sampled in a salty Tunisian soil, and the reference Jemalong A17 genotype. TN1.11 plants show increased root growth under salt stress as well as a differential accumulation of sodium ions when compared to A17. Transcriptomic analysis revealed specific gene clusters preferentially regulated by salt in root apices of TN1.11, notably those related to the auxin pathway and to changes in histone variant isoforms. Many genes encoding transcription factors (TFs) were also differentially regulated between the two genotypes in response to salt. Among those selected for functional studies, overexpression in roots of the A17 genotype of the bHLH-type TF most differentially regulated between genotypes improved significantly root growth under salt stress. Despite the global complexity of the differential transcriptional responses, we propose that an increase in this bHLH TF expression may be linked to the adaptation of M. truncatula to saline soil environments.
  Molecular Plant 03/2012; 5(5):1068-81. · 5.55 Impact Factor